Journal of Nannoplankton Research, 22, 3, 2000 .

E. She/don: A note on nannofossil preparation... , p. 199-200.

A NOTE ON NANNOFOSSIL PREPARATION OF ORGANIC-RICH
MUDSTONES USING POTASSIUM HYDROXIDEEmma She/donGeological Survey of Denmark & Greenland (GEUS), Thoravej 8, DK-2400, Copenhagen NV, Denmark

Abstract: During a recent nannofossil study of Paleocene marine mudstone from the Nuussuaq Peninsula,central W Greenland, a preparation technique using 10% potassium hydroxide was tested in order toremove amorphous organic material from the samples because this was obscuring the nannofossil
component. The test proved to be successful.

IntroductionMore than 200 dark mudstone samples were collected fromthree outcrops and four onshore wells from the Nuussuaq
Peninsula between 1990 and 1998, in order to establish arefined Lower Paleocene biostratigraphic zonation for thearea, based upon nanuofossils and dinoflagellate cysts(N0hr-Hansen et al., in press). During an initialreconnaissance of several slides, it was clear that a small
calcareous component was present, although largely
obscured by organic amorphous debris. Consequently,
conventional methods for nannofossil preparation requiredmodification.
Methodology
Initially, a standard nanuofossil preparation technique,previously used for chalk samples at GEUS, was utilised:
approximately lcm3 of sediment was crushed and added toa glass tube along with distilled water. The tube was shaken
for 15 seconds and the suspension allowed to settle for 3060 seconds. A few drops were pipetted from the middle ofthe liquid fraction, placed on a glass coverslip, spread
evenly using a toothpick and allowed to dry. Two to threedrops of Norland optical adhesive were added to thecoverslip, which was then placed onto the sample slide,
exposed to daylight (UV light) and left to cure for 24 hours.
However, this technique was modified for two main reasons:
1. the mudstones contained a hi'gh percentage oforganic matter; any calcareous material that the sample
contained was largely masked by this amorphous organicmatter; and2. the sediments were found to be rich in sulphur; waterused in the preparation of the slide is likely to react withthe sulphur in the mudstones to form sulphuric acid andthis would dissolve away any calcareous component ther;;_ample might contain.
To counteract this, the sediment was added to a 10%
potassium hydroxide (KOH) solution and allowed to standfor 3-5 minutes to remove the humic material by oxidation.
The sample was then centrifuged, decanted and a small
amount of ethanol was added instead of distilled water inorder that a potential reaction between sulphur and water
be avoided. A glass tube containing the sample was shaken
and allowed to settle before a few drops were pipetted fromthe middle part of the liquid, as before. The rest of thenannofossil slide preparation was carried out as previously
described.

Results
The samples prepared with KOH yielded poorly-preserved,
fairly low-abundance and low-diversity nannofossil
assemblages. Whole coccolith specimens were only rarelyencountered, often only outer rim-cycles or remnantsremaining, as illustrated on Plate 1, Figures 1 and 2.
However, the main organic component had beensuccessfully washed away, allowing for a more efficient
analysis of the slide than previously. Plate 1, Figure 3 shows
the degree to which the organic matter obscures thecalcareous component in an unadulterated sample. The
calcareous nannofossils appear to have been left virtuallyintact after the oxidation step.
Previous techniques
Techniques used for the breakdown of humic (amorphousorganic carbon) material have been previously describedfor palynomorph preparation (Sarjeant, 1974; Wood et al.,1996). Oxidising agents (e.g. potassium carbonate,
potassium hydroxide, sodium hydroxide, ammoniumhydroxide) were used to remove the amorphous organiccomponent. More recently, Eshet & Moshkovitz (1995)
and Eshet ( 1996) described a similar technique to prepareorganic carbon-rich sediments for nannofossil amilysis
with a 10% sodium hypochlorite solution in order to remove
the amorphous organic material.
Conclusion
The use of KOH as an oxidising agent on amorphousorganic carbon-rich mudstone samples from the Nuussuaq
Peninsula, W Greenland, enabled the recovery of asignificant amount of nannofossils. This allowed anintegration of the nannofossil biostratigraphy with thepalynological biostratigraphy and the erection of a detailed
biostratigraphic zonation ofthe Lower Paleocene, onshore
W Greenland.
Acknowledgements
Thanks go to Birte Hammerstwm for sample preparationand to Henrik N0hr-Hansen for helpful discussion. This
paper is published with permission of GEUS.
References
Eshet, Y 1996. Obtaining rich nannofossil assemblages from'barren' samples: Processing organic-rich rocks in nannofossil
investigations. Journal of Nannoplankton Research, 18(1):17-22.

199

E. She/don: A note on nannofossil preparation.. ., p. 199-200.

Journal of Nannoplankton Research, 22, 3, 2000.

Eshet, Y. & Moshkovitz, S. 1995 . New nannofossil biostratigraphy for Upper Cretaceous organic-rich carbonates inIsrael. Micropalaeontology, 40(4 ): 321-341.
N0hr-Hansen , H ., Sheldon , E. & Dam , G. In press.
Biostratigraphic dating and sedimentary evolution preluding
the Early Paleocene volcanism in central West Greenland.
Geological Society ofLondon, Special Publication.
Sarjeant, W.A.S., 1974. Fossil and Living Dinojlagellates.
Academic Press Inc., London: 132.
Wood, G.D. , Gabriel, A .M . & Lawson , J.C. 1996 .
Palynological techniques - processing and microscopy. In:
J. Jansonius & D.C. McGregor (Eds). Palynology: Principlesand Applications, 1: 29. American Association ofStratigraphic Palynologists Foundation.

PLATE ILVR = laser video record

After preparation with KOH (Kangilia outcrop; LVR 10992;Sample 369733-C780)

After preparation with KOH (Kangilia outcrop; LVRI0989;Sample 369712-cnS)

Before preparation with KOH (Well Gane #I ; LVR I0973 ;Sample E604)

200